1. Field of the invention
The present invention relates to an exterior bus for a microprocessor computer.
2. Description of the prior art
A conventional hardwear structure of multi-microcomputer system uses a plurality of CPU boards each having a central processing unit built thereon, and these CPU boards are mounted in a frame with their main surfaces parallel with each other. The lead conductors which are terminated at the inside edge of each CPU board, are connected to a bus cable extending behind the frame via an appropriate connector.
In the conventional multi-microcomputer system a plurality of CPU boards are arranged with their main surfaces parallel with each other to form a single line, and these CPU boards are connected to a single bus cable. As a consequence, the distance between two CPU boards selected among a series of boards may depend on which positions such CPU boards are located, varying greately with the increase of the number of the series-connected boards. In case of communication between selected CPU boards via the bus cable, the signal path whose length is dependent on which boards are selected, must be taken into consideration for well-timed operation.
Also, disadvantageously the transmission loss due to the stray capacitance of the bus cable will increase with the increase of signal frequency.
As shown in FIG. 9, a plurality of air conditioning fans 21 are arranged along the line of CPU boards 20. CPU boards which are positioned near each fan will be cooled more than those which are positioned far from each fan, and therefore, it is difficult that all CPU boards are cooled evenly and kept at same temperature.